1. Field of the Invention
The present invention relates to a semiconductor converter circuit and a circuit module.
2. Description of the Background Art
Semiconductor power converter circuits such as current-type inverters use switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and power MOSFETs. Further, when the converter circuits use elements substantially having no reverse breakdown voltage for use as power devices (i.e., elements of reverse conductivity type) as the switching elements, reverse blocking diodes are connected in series to the switching elements, for blocking application of reverse voltage to the switching elements. As the reverse blocking diodes, conventionally, used are rectifier diodes made of silicon which utilize a pn junction formed in a silicon substrate.
Further, high-speed diodes are sometimes used as the rectifier diodes, and in the high-speed diodes, heavy metals such as gold and platinum are diffused in the silicon substrate to reduce the lifetime of minority carriers and the reverse recovery time thereby becomes shorter.
The background-art high-speed diodes of silicon have problems that the forward voltage drop is large and the amount of reverse recovery electric charges (the time integral of reverse recovery time and reverse current) is still large. These problems lead to increased power loss and deterioration in efficiency of the semiconductor converter circuit.
An object of the present invention is to provide a semiconductor converter circuit and a circuit module both using a reverse blocking diode in which the forward voltage drop and the amount of reverse recovery electric charges are reduced as compared with the background-art high-speed diode made of silicon.
According to a first aspect of the present invention, the semiconductor converter circuit includes a switching element of reverse conductivity type and a diode made of silicon carbide. The diode is connected in series to the switching element at a polarity in which a forward current flows when the switching element comes into an ON state.
In the semiconductor converter circuit of the first aspect of the present invention, the diode made of silicon carbide is used as the reverse blocking diode connected in series to the switching element. Therefore, as compared with the semiconductor converter circuit using the diode made of silicon as the reverse blocking diode, the switching loss is remarkably reduced to improve efficiency and it is possible to prevent breakdown of the switching element by high reverse recovery voltage.
Preferably, in the semiconductor converter circuit of the first aspect, the diode is a Schottky diode.
In the semiconductor converter circuit of the first aspect of the present invention, by using the Schottky diode made of silicon carbide as the reverse blocking diode, it is possible to achieve characteristics of smaller forward voltage drop, a smaller amount of reverse recovery electric charges, higher breakdown voltage and the like and ensure further improvement of efficiency.
Preferably, in the semiconductor converter circuit of the first aspect of the present invention, the diode is connected to at least one of an anode side and a cathode side of the switching element.
In the semiconductor converter circuit of the first aspect of the present invention, by connecting the diode in particular to the anode side of the switching element, it is possible to achieve a so-called common emitter or common source circuit configuration. Therefore, by connecting the emitter or source of the switching element to a GND terminal of a control circuit, the semiconductor converter circuit and the control circuit can share the GND terminal and the circuit configuration can be thereby simplified.
Preferably, in the semiconductor converter circuit of the first aspect of the present invention, the switching element is one of an IGBT (Insulated Gate Bipolar Transistor), a power MOSFET, a bipolar power transistor, a thyristor, a GTO (Gate Turn-Off) thyristor and a GCT (Gate Commutated Turn-Off) thyristor.
In the semiconductor converter circuit of the first aspect of the present invention, it is possible to reduce the switching loss in one of the IGBT, the power MOSFET, the bipolar power transistor, the thyristor, the GTO thyristor and the GCT thyristor.
Preferably, the semiconductor converter circuit of the first aspect of the present invention is one of an inverter circuit, a converter circuit, a matrix converter circuit and an AC switching circuit.
In the semiconductor converter circuit of the first aspect of the present invention, it is possible to reduce the switching loss of the switching element used in one of the inverter circuit, the converter circuit, the matrix converter circuit and the AC switching circuit.
According to a second aspect of the present invention, the circuit module includes: a substrate on which the semiconductor converter circuit of the first aspect is formed; a package in which the substrate is provided; and a connection terminal formed on the package, for connecting the semiconductor converter circuit and an external device.
In the circuit module of the second aspect of the present invention, by modularizing the semiconductor converter circuit into the circuit module, it is possible to ensure downsizing of the device, reduction of wire inductance, simplification of control circuits and peripheral circuits and the like.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.